Art of stabilizing rayon type fabric



Patented Feb. 14, 1950 ART OF STABILIZING RAYON TYPE FABRIC Archibald S. Stevenson, Pawtucket, and Leo Beer, Providence, R. I., assignors to Alrose Chemical Company, Cranston, R.

Rhode Island I., a corporation of No Drawing. Application December 4, 1946, Serial No. 713,918

Claims.

The textile fabric with the stabilization of which the present invention is concerned, contains synthetic fibers of regenerated cellulose, such as viscose or cupra-ammonium rayon or of cellulose-acetate or other cellulose derivative, the fabric consisting of any of said fibers, alone or in admixture with one or more of the other fibers, with or without components of wool, cotton or other fiber, natural or synthetic. Fabric of the character referred to is designated hereinafter both in the specification and the claims in the interest of brevity as rayon-type fabric."

As conducive to a clear understanding of the invention, it is noted that if such rayon-type fabric were subjected to the action of caustic under conditions similar to those of mercerizing cotton, 1. e., at caustic concentration of 18 to 25 per cent in aqueous solution, at room temperature or less for a period of some minutes, great yardage loss in processing would be incurred, which in the case of spun rayon may be in the order of 20 per cent or more and may be accompanied also by excessive loss in width. Such mercerization moreover, despite the yardage loss that it entails, would be inefiicacious for stabilizing the goods since the same would shrink from 0.5 to 2 per cent more on each of several successive laundering operations. Furthermore, a considerable loss in strength and deterioration in hand and appearance of the fabric would result.

Where it is attempted to stabilize rayon fabrics by the application of unpolymerized or partially polymerized resin condensates (e. g. ureaformaldehyde or melamine-formaldehyde resins) objections arise, among which are:

a. Shrink proofing will gradually disappear as the resin is washed out through many successive launderings,

b. The fabric often acquires a stiff feel or hand" which even plasticizers or softeners will not permanently eliminate, since the latter tend to wash out in laundering,

0. Fabric so treated may retain chlorine used in certain laundering processes, with subsequent deterioration thereof,

d. Where such resin-treated fabrics are cured with strongly acid catalysts loss in abrasion resistance results,

e. The application of these resins after dyeing frequently results in change of color and sometimes in discoloration, and reduction in lightfastness,

1. Special equipment not available in some textile finishing plants is required for the high temperature baking of the resin,

g. The formaldehyde released in the application of resins to the fabric and in the subsequent curing operations is objectionable, since the odor is offensive and involves a health hazard or in the alternative, costly ventilating equipment is required, and

h. Fabrics treated with resins frequently cause dermatitis when worn by persons whose skin is sensitive to such resins.

It is among the objects of the present invention to produce textile fabrics of the rayon-type which are stabilized to a highly satisfactory degree against laundering shrinkage, without thereby incurring excessive loss of yardage and without the need to this end for incorporating in or on the fibre any foreign substance, or altering the molecular structure of the fiber or detracting from the weight or the tensile strength or the abrasion resistance of the fibre or fabric or impairing the hand of feel thereof, or objectionably detracting from its luster.

Other objects are the production of stabilized fabrics by methods readily applied with equipment now available in modern rayon finishing plants and with the use of chemicals readily obtainable at low cost and by processes simple to control with considerable economy, the saving of yardage as compared to the loss incurred in conventional pre-shrinking being suiiicient, in fact, much more than sufiicient to make up for the cost of applying the process.

Other objects are to produce controlled swelling of the rayon-type fiber in the fabric without weakening or dissolving said fiber and thereby closing the openings in the fabric and imparting thereto a fuller and richer appearance and rendering the finally dyed product more attractive in appearance.

Bearing in mind that the efiect of caustic upon rayon-type fabric becomes moderated with increase of concentration of caustic and with rise in temperature thereof, the practice of the present invention involves the treatment of the rayon-type fabric with a relatively strong solution of caustic as hereinafter more fully set forth, within predetermined limits of temperature, for a very short period of time measured in seconds rather than minutes followed by expression of excess caustic solution, and after an adequate time interval, neutralization without prior dilution of the caustic in the fabric. This is followed by rinsing, scouring and drying in the relaxed state, and finally framing to predetermined width. All of these operations are performed with minimum tension along the length of the fabric. Such treatment results in the stabilization of the fabric against shrinkage in subsequent laundering operations and such stabilization occurs with little or no loss in efiective length of the fabric as compared with the loss of as much as 20 to 25 per cent in such effective length that is incurred where mercerization in the usual sense of the term is resorted to.

The caustic agent used may be potassium hydroxide or lithium hydroxide or mixtures thereof with or without sodium hydroxide, but for reasons of economy sodium hydroxide is preferred. An aqueous solution of the sodium hydroxide or other caustic alkali is applied at a concentration of 30 to 50 per cent at a temperature in the range of 15 to 80 degrees C. Preferably the concentration is between 30 and 40 per cent and the temperature between 20 and 60 degrees C. Where a concentration of 30 per cent of caustic is used the preferred temperature is 40 to 60 degrees C.; where 40 per cent caustic is used, it is preferably 20 to 35 degrees C., but may be higher, if acetate or wool fibers are not present, since the effect of temperature on viscose rayon is less critical at this concentration.

The caustic solution is applied to the fabric preferably by passing the latter through a bath of such solution in such manner that no part of the fabric remains immersed for a period more than a few seconds, preferably not more than 2 or 3 seconds. The fabric is then squeezed on the padder or quetsch to insure thorough impregnation and removal of excess caustic solution. Thorough saturation in the very short period of immersion is assured by adding to the bath .5 to 1.5 per cent, preferably about 1 per cent of a suitable wetting agent which may be a phenolic compound, (phenols, cresols, xylenols or mixtures thereof) with a solvent, desirably ethylene glycol mono-butyl ether. For a 40 per cent caustic bath, a wetting agent of 94 per cent phenol and 6 per cent of said solvent is especially eiiicacious.

The short period of immersion set forth varies substantially inversely with the speed of penetration of caustic into the fabric.

After squeezing out excess caustic impregnating solution on the padder or quetsch, the fabric still retains about 60 to 100 per cent of its weight of caustic solution. This corresponds to approximately 20 to 50 per cent of actual caustic alkali (as dry hydroxide) based on the weight of the fabric. Commercial runs with 25 to 50 per cent of actual NaOH (calculated as dry hydroxide) on the fabric after squeezing have produced adequate stabilization.

After the goods have been impregnated with caustic, and the excess squeezed out, as set forth, the fibers assume a semi-plastic state and therefore the goods should not be put through nips or allowed to wrinkle at this stage. Nor should water drops be permitted to fall on the fabric before or after impregnation, since noticeable defects would become apparent upon dyeing. For this reason the fabric must be handled in the open width until it is neutralized, after which stage it may be handled in rope form or open width as desired.

After the caustic treatment the fabric is skyed, that is, run in a span through air from the caustic padder to the neutralizing bath for a period such that the total time elapsed from the entry into the caustic bath to the entry into the neutralizing bath is from to 50 seconds or more, and the skying time is therefore slightly less by the few seconds of immersion. If the fabric after excess caustic solution has been squeezed out is batched or rolled rather than "skyed (as may be required if continuous processing equipment is not available) it may be left for a longer period of time before neutralizing without adverse efl'ect.

After the "skying or batching operation, the fabric is run directly into the neutralizing bath. Dilute acids are used for neutralization, prefer- 4 ably a 5 to 10 per cent solution of sulphuric acid at about 15 to 60 degrees 0., but hydrochloric or acetic acid may be used if desired. It is also feasible to use a hot saturated solution of sodium bicarbonate at a temperature of 40 to degrees (1.. preferably of about 60 degrees C.

Were it attempted to wash out the caustic by a water treatment rather than by neutralization, swelling, parchmentizing and serious loss in tensile strength would be incurred, especially as the caustic concentration passes through the critical range of between 6 and 14 per cent NaOH.

After neutralization, rinsing of the fabric is effected, preferably in a sequence of aqueous baths, some hot, some cold, to remove residual alkali and salts, followed by withdrawal of excess moisture by pressure, centrifugation or vacuum extraction.

The fabric in rope form is then passed through a beck where it is desized and scoured. Thereupon, the goods are dyed and rinsed on the beck, or they may be opened out, dried and dyed or printed in the opened width.

It is important that each of the foregoing steps, 1. e., the caustic treatment, the neutralization, the rinsing, desizing and scouring, the moisture withdrawal, the dyeing following by rinsing and drying be performed with the fabric under little or no lengthwise tension.

Finally the slack dried fabric is given a laundering test which is preferably more severe than ordinarily given to synthetic fabrics. In fact the standard wash test for cotton fabrics is preferred, in which the material is laundered at the boil (See Yearbook of the American Association of Textile Chemists and Colorists, 1945, page 219). The laundering shrinkage in warp and filling is measured and the required finished width for zero shrinkage is computed.

After padding the fabric through water with appropriate softening, stiffening or other finishing agents, the fabric is dried on the tenter frame to the proper width. Alternatively, it may be relax-dried again, then steamed and framed to the required width. Should there be some small residual warp-wise shrinkage in the laundering test, mechanical overfeed devices which are available for tenter frames may be resorted to. By way of example, the fabric may be given a further relaxation treatment on the beck, then slack dried, steamed and framed to proper width, with the required degree of overfeed.

Our process has been successfully applied to fabric made of yarn of filament or spun staple fibers which are of regenerated cellulose (viscose or cupra-ammonium), acetate rayon (cellulose acetate), and mixtures of these synthetic fibers with cotton, wool or other fibers, natural or synthetic, or with each other. As above noted, these fabrics are briefly designated as rayon type fabrics."

By treating the rayon-type fabric with caustic within the limited range of concentration and within the limited range of temperatures and for the duration of treatment noted, and by conducting said treatment as well as the neutralization and the other steps in substantially the absence of tension all as heretofore set forth, the present invention avoids the excessive and economically wasteful contraction in length and width incurred where the lower concentrations and lower temperatures of caustic are used, especially for the longer periods of time commonly resorted to in mercerization practices. In fact, according to the present process, the warp-wise contraction is ordinarily per cent or less and in some cases may be entirely absent. Yet the fiber is in no wise impaired, insofar as its tensile strength, its abrasion resistance and its luster are concerned, nor is there any increase in the extensibility or elasticity of the fiber or fabric as compared to the untreated product.

It is frequently preferred to apply the process directly to grey goods of the rayon type as received from the mill. The goods may be kept at their original width by means of expanders before and after entering the padders, resulting in stabilization at a width more nearly equal to the grey width. Also the length of the fabric is much nearer to its original dimensions and much less loss in yardage is incurred than if the grey goods were first scoured, a step which is moreover eliminated according to this procedure.

The treatment of the unpreshrunk grey goods, according to th foregoing process, thus accomplishes the dimensional stabilization above set forth with a total loss in yardage as above set forth of only 5 per cent on the unpreshrunk grey goods as compared with the loss of per cent or more in the case of filament rayon fabrics or of as much as per cent in spun rayon fabrics finished by ordinary processing methods which do not result in stabilization.

While the theory by which we explain the mechanism or mode of operation of our process may not be correct, and we do not wish to be bound thereby, we believe that the caustic treatment under carefully controlled conditions of time, temperature and concentration results in only slight swelling and plasticization of the fiber, suificlent merely to relax the mechanical strains that had been imposed on the fibers in the course of the twisting of the synthetic yarn and on the yarn and its component fibers in the weaving or the knitting of the fabric therefrom. Since further handling of the goods is accomplished with minimum tension to avoid stresses which might again introduce strains similar to those which had been already removed, the fabric remains completely relaxed, and subsequent launderings may be carried out without further contraction or shrinkage. The treatment set forth, it is believed, has in some way permitted molecular or micellar rearrangement to a strain-free condition and this without chemically changing the fiber or leaving any ingredient therein, or for that matter, effecting any physical change other than slight swelling of the fiber. Therefore, aside from the other advantages pointed out, the product does not suffer weakening or disintegration.

While satisfactory results are attained by the procedure as above described, improvements in results are attained, by further moderating the effect of the caustic solution upon the fabric by use of a protective agent, that will further llrnit the attack of the caustic upon the fabric and will further limit the swelling action upon the fiber, and improve the hand or feel of the fabric. This protective agent may be preliminarily applied to the fabric from solution and dried thereon before the caustic treatment, but in the interest of economy it is preferred to include such protective agent in the caustic solution and thereby to apply concurrently to the fabric the protective agent as well as the caustic.

In the latter and preferred procedure, as the protective agent, there is admixed with the caustic, sodium silicate solution, desirably 2 to 10 per cent and preferably 5 per cent by weight, which latter amounts to about 2 per cent of actual sodium silicate by dry weight. The sodium silicate apparently depresses the ionization of the caustic and also acts as a protective colloid; possibly it may also protect the fiber during neutralization due to deposition of colloidal silica thereon.

Where the protective agent is applied to the fabric from aqueous solution and dried thereon prior to the caustic treatment, it may contain materials in any of the following categories:

a. Salts of amphoteric metals such as zinc sulphate, aluminum sulphate, sodium stannate, and sodium silicate (in the case of strongly acid salts such as zinc sulphate and aluminum sulphate, a buffer, such as urea, is employed to prevent deterioration of the fabric while drying).

b. Salts which tend to repress the ionization of caustic, including sodium chloride, sodium sulphate, potassium chloride, potassium sulphate and borax.

c. Salts of organic carboxylic or sulfonic acids of the aromatic or aliphatic series, such as sodium benzoate, sodium naphthalene sulphonate or resin acid soaps such as sodium abietate or fatty acid soaps.

d. High molecular organic compounds forming protective colloids and not readily attacked under the conditions of treatment described, by sodium hydroxide, such as methyl cellulose, salts of carboxymethyl cellulose, gelatin, soy bean protein or mixtures of the same.

e. Polyhydric alcohols, carbamides or mixtures thereof and among which are glycerols, glycols, polyglycols and urea.

A desirable protective agent for this mode of application consists of a mixture of either protein or carboxymethyl cellulose admixed with either urea or borax.

The concentration of caustic, temperature, time of treatment, charatcer of wetting agent and of protective agent used, and the like will of course be varied in manner within the scope of those skilled in the art, depending on the fabric to be treated and the result to be accomplished. There are a number of specific examples outlined below:

Example 1 A caustic impregnating bath of the following composition by weight is prepared and allowed to cool before use:

Caustic soda, as NaOH 30 to 50% as per schedule below Sodium silicate, as NazSiOa 2.5

Phenol 0.93%

Ethylene glycol monobutylether 0.06%

Water .66.5 to 46.5%

The temperature and concentration limitations vary depending on the type of fabric employed and the effect desired, thus:

The fabric (in the grey, scoured, or vat-dyed state) under minimum warp tension, is immersed in the open width in the above solution for 1 to 2 seconds, and squeezed on a padder or quetsch to about 90% liquid pickup based on the weight of dry fabric. After skying, for 10 to 20 seconds, the fabric is immersed in a large volume of to per cent sulfuric acid solution, then washed with water, neutralized in 5 per cent to 6 per cent hot sodium bicarbonate solution, and rinsed.

The above operations are carried out on a continuous processing unit comprising a padder followed by a set of skying rollers and a multicompartment open-width washer, containing, in consecutive compartments: (1) dilute sulfuric acid, (2) water, (3) sodium bicarbonate solution, (4) hot water, (5) cold water.

The goods are then scoured in rope form in the beck, first in boiling soap solution, then in cold water. The fabric is opened, extracted, and slack-dried in the loop drier.

At this stage, a laundering test is run on a portion of the goods to determine whether relaxation is sufficient and to determine the proper width for zero shrinkage.

Where the goods have been dyed or printed before stabilization, they are merely steamed and framed to the predetermined width. If grey or scoured goods have been used in the stabilization process, they are then dyed, scoured, extracted and slack dried again before framing to the proper width.

The above procedure is suitable for stabilization of all types of rayon and mixed fabrics. Using 40 to 50 per cent caustic at to degrees C., cellulose acetate may be treated without saponification, and fabrics containing wool or regenerated protein fibers may be treated without loss in protein content, and without damage to the wool fibers.

Fabrics when treated by the above procedure become stabilized to a laundering shrinkage of less than 2 per cent. The same fabrics treated by the customary rayon finishing methods show shrinkage of 10 per cent to 20 per cent on laundering.

Example 2 Example 3 Rayon-type fabrics are precoated by impregnating with an aqueous solution containing a mixture of:

2.5% 0.5% 2.5% urea 0.5% trisodium phosphate The fabric is squeezed to a pickup of 90 to 100 per cent and dried on a tenter-frame at grey goods width. It is then impregnated with a 30 to 50 per cent caustic soda solution on the padder and skyed and neutralized as described in Example 1.

Excellent stabilization is obtained by this procedure with no loss in strength or deterioration in hand or appearance of the fabric.

soybean protein aluminum cellulose glycollate Example 4 Rayon-type fabrics are treated by a procedure corresponding to Example 1, except that 40 to 45 per cent caustic soda is used alone, without addition of protective agents or penetrants, as the swelling agent.

Stabilization as good as that of Example 1 is obtained. The hand is firmer and slightly harsher, and, hence, this procedure is applicable only on fabrics where a firmer hand is desired. It has been used with satisfactory results on heavy twill fabrics and on part wool fabrics to enhance the woolly hand.

Example 5 Spun rayon or filament rayon fabrics are treated as in Example 3, using 30 per cent caustic soda at 55 degrees C. Results are similar to Example 3 except that a firm, crisp hand is obtained.

Example 6 This method gives satisfactory stabilization on spun and filament viscose rayons and on cotton and viscose mixtures and is resorted to when continuous equipment is not available. A rayontype fabric impregnated with caustic soda solution as in any of the foregoing examples, instead of skying is batched onto rolls after leaving the caustic padder.

The roll of cloth is then neutralized on a jig or open-soaper and washed as in Example 1.

The above examples describe actual commercial applications of our process. Other combinations of concentrations, temperatures, and protective and penetrating agents, within the limitations herein described, will occur to those versed in the art, and may be used to vary the hand or finish or to adapt the process to the equipment available.

While stabilization is accomplished in our process without requiring deposition of any foreign material in or on the fiber, the finisher is free to add any finishing agents he desires to obtain effects other than stabilization. Thus, he may employ resins for stiffening the fabric or imparting crease-resistance or he may use other stiffening or softening agents without departing from the spirit of this invention.

As many changes could be made in the above process and product and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. The process of treating textile fabric of rayon type by subjecting the fabric while maintained in the open width to aqueous solution of caustic alkali in concentration of 30 to 50 per cent at a temperature of 20 to 60 degrees C. for a period of time varying substantially inversely with the speed of penetration of caustic into the fabric, said period of time being but a few seconds where the fabric is rapidly saturated with said caustic solution, squeezing until the fabric retains 60 to per cent of caustic solution based on the fabric weight, and, within a period well under one minute after the start of the caustic impregnation, neutralizing directly without prior dilution of the caustic in the treated fabric, washing the fabric substantially to free it of the neutralized impregnating agents, drying the fabric and adjusting to predetermined width, all of said steps being performed under substantially slack condition of the length of the fabric with resultant stabilization at a length contraction materially less than that incurred in conventional shrinkage treatment.

2. The process of treating textile fabric of rayon type, which comprises the impregnation of the fabric in a bath containing caustic alkali of 30 to 50 per cent concentration at a temperature of to 60 degrees C. for a period of not more than a few seconds, squeezing out excess caustic and passing the caustic impregnated fabric through air for a period well under one minute after the start of the caustic impregnation and thereupon passing the same through a neutralization bath while msintaining it in the open width, washing the fabric substantially to free it from the neutralized impregnating agents, drying it and adjusting to predetermined width, all of said steps being performed under substantially slack condition of the length of the fabric with resultant stabilization at a length contraction materially less than that incurred in conventional shrinkage treatment.

3. The process claimed in claim 2. in which the caustic alkali is sodium hydroxide of about 30 per cent concentration applied at a temperature of 40 to 60 degrees C.

4. The process claimed in claim 2, in which the caustic alkali is sodium hydroxide of about 40 per cent concentration applied at a temperature of 20 to 60 degrees C. and the fabric is squeezed to ensure thorough impregnation and to remove excess caustic solution.

5. The process recited in claim 1, in which after washing, color is applied to the fabric under minimum tension thereon, and the fabric is then dried without tension and adjusted to predetermined width.

6. The process of treating textile fabric of rayon type, which comprises the impregnation of the fabric in a bath containing caustic alkali of about 40 per cent concentration at a temperature of 20 to 60 degrees C. for a period of not more than a few seconds, squeezing excess caustic from the fabric, passing it through the air for a period well under one minute after the commencement of the impregnation and thereupon impregnating the fabric in a neutralizing solution, washing the fabric substantially to free it of the neutralized impregnating agents, drying it and framing to predetermined width, all of said steps being performed under slack condition of the length of the fabric with resultant stabilization at a length contraction materially less than that incurred in conventional shrinkage treatment.

'1. The process recited in claim 6 in which the residual alkali and salts are removed in a succession of water washes and in which the washing is conducted upon the fabric in rope form under slack conditions and the drying and subsequent application of coloring are effected under relatively slack condition.

8. The process of treating textile fabric of rayon type, which comprises subjecting the fabric to aqueous caustic alkali in concentration of 30 to 50 per cent at a temperature of 20 to 60 de grees C. performed in the presence of protective agent serving to moderate the intensity of the action of the caustic upon the fabric and for a period of timevarying substantially inversely 10 with the speed of saturation of the fabric by the caustic, said period of time being but a few seconds where the fabric is saturated with caustic rapidly, squeezing to remove excess alkali, and within a period well under one minute after the beginning of caustic impregnation effecting neutralization of the caustic treated fabric, the washing of the fabric substantially to free it of the impregnating agents and the drying of the fabric and adjustment to predetermined width, all of said steps being performed under substantially slack condition of the length of the fabric with resultant stabilization at a length contraction materially less than that incurred in conventional shrinkage treatment.

9. The process of treating textile fabric of the rayon type, which comprises subjecting the fabric to aqueous caustic alkali in concentration of 30 to per cent at a temperature of 20 to degrees C. in the presence of a protective agent serving to moderate the intensity of the action of the caustic upon the fabric, comprising between 1 and 5 per cent of sodium silicate admixed in solution with the caustic and for a period of time varying inversely with the speed of penetration of caustic to the fabric, said period of time being but a few seconds where the fabric is rapidly saturated with caustic, squeezing out excess caustic and within a period well under one minute after the beginning of caustic treatment effecting, the direct neutralization of the caustictreated fabric, the washing of the fabric substantially to free it of the impregnating agents and the drying of the fabric, and adjustment to predetermined width, all of said steps being performed under substantially slack condition of the length of the fabric with resultant stabilization at a length contraction materially less than that incurred conventional shrinkage treatment.

10. The process recited in claim 9, said solution containing about 2 per cent by weight of sodium silicate admixed in solution with the caustic.

11. The process of stabilizing textile fabrics of the rayon type in the unshrunk grey goods stage, which comprises saturating the goods with aqueous solution of caustic in concentration of 30 to 50 per cent at a temperature of 20 to 60 degrees C. for a period of not more than a few seconds, squeezing out the excess caustic solution and thereupon within a period well under one minute after the start of the caustic impregnation, treating the fabric in neutralizing solution, and then washing and scouring the fabric for removal of substantially all of the neutralized treating agents. and adjusting to predetermined width, all of said processes being con ducted on the substantially slack condition of length of the fabric with resultant stabilization and.1ength contraction materially less than that incurred in conventional preshrinking.

12. The process of treating textile fabric of rayon type by impregnating the fabric in aqueous solution of caustic alkali in concentration of 30 to 50 per cent at a temperature of 20 to 60 degrees C. for not more than a few seconds, squeezing out the excess caustic solution, batching the fabric and thereafter in regular course of handling, subjecting the fabric to neutralization, washing substantially to free it of the neutralized impregnating agents, drying the fabric and framing to predetermined width, all of said steps being performed under substantially slack condition of the length of the fabric with resultant stabilization at a length contraction ma- 11 terially less than that incurred in conventional shrinkage treatment.

13. The process recited in claim 1 in which the speed of penetration of the caustic solution into the fabric is expedited by the addition to the bath of a wetting agent in proportion of about .5 to 1.5 per cent by weight.

14. The process recited in claim 1 in which the speed of penetration of the caustic solution into the fabric is expedited by the addition to the bath of a wetting agent in proportion of about .5 to 1.5 per cent by weight, said wetting agent being a phenolic compound with a solvent of ethylene glycol monobutyl ether.

15. The process of treating textile fabric of the rayon type, which comprises immersing the fabric in a solution of an aqueous caustic alkali in concentration of 30 to 50 per cent containing also a protective agent comprising between 1 and 5 per cent of sodium silicate and a wetting agent in percentage of .5 to 1.5 per cent at a temperature of 20 to 60 degrees C. for a period of time not exceeding 3 seconds, squeezing out excess caustic and thereupon within a period well under one minute after the start of caustic impregnation directly neutralizing the caustic treated fabric, washing it substantially to free it of the impregnant, drying it, and adjusting to prede- 12 termined width, all of said steps being performed under substantially slack condition of the length of fabric with resultant stabilization at a length contraction materially less than that incurred in conventional shrinkage treatment.

ARCHIBALD S. STEVENSON. LEO BEER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,851,914 Lier Mar. 29, 1932 1,989,098 Lilienfeld Jan. 29, 1935 1,989,100 Lillenfeld Jan. 29, 1935 1,989,101 Lilienfeld Jan. 29, 1935 2,112,499 Lilienfeld Mar. 29, 1938 FOREIGN PATENTS Number Country Date 437,485 Great Britain Oct. 30, 1935 462,899 Great Britain Mar. 1'1, 1937 501,768 Great Britain Mar. 6, 1939 546,673 Great Britain July 24, 1942 560,378 Great Britain Apr. 3, 1944 

1. THE PROCESS OF TREATING TEXILE FABRIC OF RAYON TYPE BY SUBJECTING THE FABRIC WHILE MAINTAINED IN THE OPEN WIDTH TO AQUEOUS SOLUTION OF CAUSTIC ALKALI IN CONCENTRATION OF 30 TO 50 PER CENT AT A TEMPERATURE OF 20 TO 60 DEGREES C. FOR A PERIOD OF TIME VARYING SUBSTANTIALLY INVERSELY WITH THE SPEED OF PENETRATION OF CAUSTIC INTO THE FABRIC, SAID PERIOD OF TIME BEING BUT A FEW SECONDS WHERE THE FABRIC IS RAPIDLY SATURATED WITH SAID CAUSTIC SOLUTION, SQUEEZING UNTIL THE FABRIC RETAINS 60 TO 100 PER CENT OF CAUSTIC SOLUTION BASED ON THE FABRIC WEIGHT, AND, WITHIN A PERIOD WELL UNDER ONE MINUTE AFTER THE START OF THE CAUSTIC IMPREGNATION, NEUTRALIZING DIRECTLY WITHOUT PRIOR DILUTION OF THE CAUSTIC IN THE TREATED FABRIC, WASHING THE FABRIC SUBSTANTIALLY TO FREE IT OF THE NEUTRALIZED IMPREGNATING AGENST, DRYING THE FABRIC AND ADJUSTING TO PREDETERMINED WIDTH, ALL OF SAID STEPS BEING PERFORMED UNDER SUBSTANTIALLY SLACK CONDITION OF THE LENGTH OF THE FABRIC WITH RESULTANT STABILIZATION AT A LENGTH CONTRACTION MATERIALLY LESS THAN THAT INCURRED IN CONVENTIONAL SHRINKAGE TREATMENT. 